CVE-2006-0451 in Fedora Core
Summary
by MITRE
Multiple memory leaks in the LDAP component in Fedora Directory Server 1.0 allow remote attackers to cause a denial of service (memory consumption) via invalid BER packets that trigger an error, which might prevent memory from being freed if it was allocated during the ber_scanf call, as demonstrated using the ProtoVer LDAP test suite.
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Analysis
by VulDB Data Team • 08/04/2017
The vulnerability identified as CVE-2006-0451 represents a critical memory management flaw within the LDAP component of Fedora Directory Server version 1.0. This issue stems from improper handling of malformed Basic Encoding Rules (BER) packets during the LDAP protocol processing. The vulnerability specifically affects the ber_scanf function which is responsible for parsing BER encoded data structures commonly used in LDAP communications. When the server encounters invalid BER packets, the error handling mechanism fails to properly release memory that was allocated during the parsing operation, leading to progressive memory consumption over time.
The technical implementation of this vulnerability leverages the ProtoVer LDAP test suite to demonstrate the memory leak behavior. During normal LDAP operations, the ber_scanf function allocates memory buffers to store parsed data structures. However, when malformed BER packets are received, the error path does not properly execute the memory cleanup routines that should occur after allocation. This creates a condition where allocated memory remains unreleased even after the error handling completes, causing gradual memory exhaustion. The vulnerability manifests as a denial of service condition where the server's memory usage continuously increases until system resources are depleted, ultimately preventing legitimate service operations.
From an operational perspective, this vulnerability presents significant risk to directory services infrastructure as it allows remote attackers to consume system resources without requiring authentication or specific privileges. The memory leaks occur during the processing of LDAP bind operations and other protocol exchanges, making the attack surface quite broad. The vulnerability is particularly concerning because it can be exploited through simple network traffic without requiring specialized tools or deep protocol knowledge. Security teams must consider that this flaw can be leveraged in automated attack scenarios where multiple connections are established to gradually exhaust system memory resources, potentially leading to complete service unavailability.
The vulnerability aligns with CWE-401, which specifically addresses memory leaks in software systems, and demonstrates characteristics consistent with the ATT&CK technique T1499.004 for network denial of service attacks. Organizations running Fedora Directory Server 1.0 should implement immediate mitigations including applying the vendor-provided patches, implementing network-level rate limiting to prevent abuse, and monitoring memory consumption patterns to detect potential exploitation attempts. Additionally, network segmentation and access controls should be strengthened to limit exposure to potentially malicious actors. The root cause requires code-level fixes to ensure proper memory cleanup in error handling paths, particularly around the ber_scanf function calls, to guarantee that all allocated memory is properly freed regardless of processing outcomes.